The present invention relates to a control apparatus and method for an automatic transmission, capable of judging an occurrence of judder due to self-excited vibration.
U.S. Pat. No. 6,024,674 (Japanese Patent Application publication No. 10-159872) discloses a previously proposed control apparatus equipped with a judder judging means for judging an occurrence of judder due to self-excited vibration. In this technique, a fluctuation in an output-shaft rotational speed of a friction clutch is detected. Then, on the basis of a frequency component (first or second frequency component) obtained by applying a filtering process to this rotational fluctuation, it is judged whether this rotational fluctuation is due to the self-excited vibration (judder) or due to a disturbance.